DAKTNS : SHAP GRANITE BOULDERS. 
65 
in striking contrast to the upper. It seems odd that the two 
should be of such different colours, as the materials of both 
are derived from the neighbouring mountains. It strikes 
me that the following may be the cause of this marked 
difference. There are spaces of considerable extent among 
the mountains, where the rocks are stained deep red; this is 
due to the oxidation of iron ; and I have noticed that such 
rocks are far more disintegrated than others. It seems as if 
the irony rocks were more easily acted on by the weather 
than the less irony. This being the case, there must have 
been a greater proportion of red detritus ready for removal 
when the ice age came on : and as the moving ice would first 
sweep away the weathered rocks forming the surface before 
it began to attack the solid unweathered rocks, we might 
expect that the earliest formed Drift would be of a red hue, 
as containing a greater proportion of red detritus than the 
last formed, which was derived from rocks previously un- 
weathered. 
In conclusion, I will make one remark, which seems to 
be called for, on weathered rocks. We read over and over 
again of an upper yellow, or reddish, and a lower blue 
boulder clay, and on this difference of colour is founded a 
division of a boulder clay into two distinct formations ; and 
I know not what deductions are made therefrom. Of course 
there may be a boulder clay of an original yellow or red 
colour, as I believe the one at Grasmere to be ; but in all the 
cases that I have seen of an upper yellow, or reddish, and a 
lower blue clay, the upper is merely the weathered part of 
the blue clay. It is the same with any blue rock, Go into 
any quarry of blue stone, and you will find that, while the 
heart of the stone is blue, the outer part is yellowish or 
reddish. 
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